1. Field of the Invention
The present invention relates to optical fiber conductors of glass type. In the present invention the optical fiber conductors include as embodiments thereof single optical fibers comprising a core and a cladding layer formed on the core and furthermore, if necessary, a supporting layer formed on the cladding layer, and also include as other embodiments thereof multiple optical fibers wherein a plurality of single optical fibers are fused and joined to one another. The single optical fibers of the present invention are suited for optical telecommunication and illumination, while the multiple optical fibers are suited an image transmitters.
The present invention also relates to image scopes which incorporate the above multiple optical fiber as an image transmitter and are suited for industrial, medical and other uses.
2. Prior Art of the Invention
Single optical fibers and also multiple optical fibers of glass type have been required to be more and more small in outer diameter thereof, as far as they can satisfy a required optical transmitting characteristics. For instance, in the case of an optical fiber cable for telecommunicational uses comprising single optical fibers, the smaller the outer diameter of each single optical fiber is, the smaller the finished outer diameter of the optical fiber cable, and as a result it become possible to install more of the cables in a limited space. On the other hand, is the case of an image scope incorporating a multiple optical fiber as an image transmitter, such a sope is required for directly observing in detail portions or sites which are usually difficult to observe, such as the interior of hot blast furnaces, the interior of atomic reactors exposed to radiation, internal portions of the human body or animals, nallow or constricted inner portions of devices, etc.
Optical fiber conductors of glass type are in general produced by drawing a preform or a bundle of preforms at high temperature and then applying a fiber-reinforcing layer on the fiber thus drawn. As a material of the fiber-reinforcing layer it has been employed organic resins, such as a thermoplastic resin, a thermosetting resin etc. It is, however, difficult to form a thiner fiber-reinforcing layer without inclination or unevenness in thickness. Accordingly, as far as a fiber-reinforcing layer made of organic resin is adopted, there is inevitable limitation for reducing the outer diameters of optical fiber conductors as well as the outer diameters of image scopes.